The wind turbines comprise a tower, a nacelle which houses the electrical generator and a rotor formed in turn by at least two blades. The tower of the wind turbine supports the nacelle and the rotor. Large wind turbines have steel, lattice, or reinforced concrete towers or even mixed-type towers, the latter comprising sections of different materials, for example, a lower section of concrete and an upper section of steel or lattice.
The larger the diameter of the rotor, the higher the rated power of the wind turbines which in turn involves the use of higher towers. The increase in tower height may necessarily require that the tower be divided into several annular sections which are stacked during the wind turbine assembly stage thus forming the full height of the tower. Dividing the tower into sections has the advantage that each section has a size such that its transport by road or rail is easier.
One of the most commonly used materials for large towers is concrete, since it involves acceptable production costs compared to those for the production of steel towers of similar characteristics. However, the weight of each concrete tower section can easily exceed one hundred tons, this fact being infrequent for metal tower sections, so stacking the concrete sections requires heavy-tonnage lifting and positioning means. The cost of using such lifting and positioning means, which may be for example a crane, is directly related to the tonnage that it is capable of handling and the time of use thereof. This high-tonnage crane is also used for lifting and positioning the nacelle, as the weight of the nacelle may also exceed 100 tons.
The design of wind turbine components and the design of the connections between them once placed, should take into account the loads they will be subjected to throughout their useful life to ensure the proper functioning thereof. In particular, the connections between different sections comprising concrete are adapted to withstand the loads induced by the rotor, these being the loads resulting from the wind falling on the surface of the rotor and the rotor weight loads.
It is known in the prior art that the procedure for assembling a wind turbine comprises the following stages:                Stacking each upper annular section onto the lower annular section by using lifting and positioning means;        Performing the connection between both upper and lower annular sections, connection meaning that which is adapted to withstand loads induced by the rotor;        Repeating the above steps for all the sections of the tower;        Stacking the nacelle onto the upper annular section;        Performing the connection between the nacelle and the upper section, the connection being adapted to withstand loads induced by the rotor.        
This method for the assembly of wind turbines has the disadvantage that the use of the crane involves a lot of time since the connecting of sections takes a long time, i.e. the hardening of the binding material takes time, and meanwhile the crane is inactive.